1. Field of the Invention
The present invention is concerned in general terms with a declutching mechanism having a clutch release bearing, for working in traction on the connecting piece of a clutch.
2. Description of the Prior Art
Such a mechanism is described in the document FR-A-2 304 826. In this document the connecting piece, constituting a declutching ring, is part of a primary block which includes the engine and its clutch.
The piece is suitably carried on the declutching means of the clutch, typically the fingers of a diaphragm. The clutch release bearing is part of a secondary block which comprises the gearbox with its input shaft. The release bearing is mounted for axial movement along a guide tube, under the action of a declutching fork which is mounted pivotally on a casing hood fixed to the gearbox.
Tractive coupling means, having a radially elastic coupling member, are arranged between the connecting piece and an actuating member which is part of a clutch release bearing.
Thus, during the assembly operation, it is necessary to bring the primary and secondary blocks axially towards each other in order to proceed with fitting them together by snap-fitting or clipping. In this connection, bosses are arranged on the release bearing so that the fork can also drive the release bearing in the opposite direction to the normal declutching direction.
Thus, by uncoupling the fork from the control linkage, it is possible, due to the coupling member, to cause the fork to deflect in the opposite direction for the purposes of carrying out the blind snap-fitting of the clutch release bearing with the connecting piece.
These arrangements cannot be used when the clutch release bearing is attached to a hydraulic actuator. For example, as described in the document FR-A-2 651 846, the declutching mechanism, for working in traction on the connecting piece of a clutch, in particular for a motor vehicle, includes firstly, a hydraulic actuator comprising at least one fixed member and a movable member in piston and cylinder relationship so as to define a first control chamber, and secondly, a clutch release bearing attached to the movable member and manoeuvrable by the latter in a first axial direction referred to as a declutching direction, for transmitting a tractive declutching force to the connecting piece.
In that document, in order to permit snap-fitting assembly, an abutment is provided which prevents the clutch release bearing from moving during the fitting operation.
This abutment is part of a rod having a V-shaped groove at its end.
The rod is fixed to a piston, which is displaceable within a cylinder defined by a protuberance of the fixed part of the actuator. This rod is acted on by a spring. During the fitting operation, the clutch release bearing is first retracted manually, and the piston is then displaced manually to cause the abutment to emerge. Afterwards, the spring maintains the release bearing in position.
After the clutch mechanism has been fitted to the connecting piece, a pressure is applied from a master cylinder through a duct in order to retract the rod and the abutment.
All of these arrangements are complicated, take a long time to carry out, and are not compatible with blind fitting. They lead to an increase in they size of the fixed member of the actuator.